JP4080486B2 - Method for forming magneto-optical recording medium - Google Patents

Description

  The present invention relates to a magneto-optical recording medium and a method for forming the same, and more particularly, to a magneto-optical recording medium that performs reproduction using movement of a domain wall and a method for forming the same.

Conventionally, a magneto-optical recording medium that records and reproduces information by irradiating a light beam has been put to practical use. However, in order to improve the reproducing characteristics of a recording medium with a high density, the movement of the domain wall is used. A reproduction-type magneto-optical recording medium has been proposed (for example, Japanese Patent Application Laid-Open No. 6-290496).
This document includes three magnetic layers that are sequentially stacked. The first magnetic layer has a relatively small domain wall coercive force compared to the upper third magnetic layer, and the second magnetic layer includes the first and third magnetic layers. A magneto-optical recording medium is described in which the Curie temperature is lower than that of the magnetic layer, the third magnetic layer has a relatively large domain wall coercive force, and is a perpendicular magnetization film having a high Curie temperature.
Here, by raising the temperature to near the Curie temperature of the second magnetic layer by irradiation with a light beam, the exchange coupling between the first and third magnetic layers is broken, and the domain wall at the boundary portion of the recording mark is It is moved by the temperature gradient.
And the magnetization reversal of the 1st magnetic layer which arises by this domain wall movement is detected as a change of a magneto-optical signal, and information is reproduced.
In this reproducing method, it is desirable that the domain wall at the front boundary part and the domain wall at the rear boundary part of the recording mark are formed separately and independently in order to stabilize the movement of the domain wall and improve the reproduction characteristics.
Therefore, in order to ensure separation of the domain walls, conventionally, after the magnetic film is formed, the guide groove portions on both sides of the track are annealed with a high-power laser to alter or disappear the magnetic film on the track side portion. After that, a recording mark is formed to separate the front and rear domain walls.
In addition, an optical memory element in which a magnetic layer formed on a side wall portion between a land and a groove is oxidized in order to separate a domain wall at the boundary between the land and the groove has been proposed (see Japanese Patent Application Laid-Open No. 2000-235743).
Here, after forming a magnetic layer over the entire land and groove, a selective oxidation layer made of Si is formed on the magnetic layer in a state where argon gas is introduced, and is further maintained in the atmosphere for a long time. The magnetic layer formed on the side wall is selectively oxidized.

Problems to be solved by the invention

However, in the magneto-optical recording medium described in the conventional literature, it is necessary to perform laser annealing on each disk after the disk is formed. Therefore, the disk manufacturing process becomes complicated and the laser annealing process is performed, so that the manufacturing stability is not sufficient and the manufacturing cost is increased. Further, there is a problem that this manufacturing method cannot be applied to a so-called land-groove substrate which can be further densified.
Further, in the conventional optical memory element, in order to selectively oxidize the magnetic layer on the side wall portion, a process for forming an unnecessary selective oxidation layer on the completed medium, or after being left in the atmosphere for a long time, or oxygen Since it is necessary to perform selective oxidation treatment with plasma, the manufacturing process is complicated and takes a long time, which causes an increase in manufacturing cost.

In this invention, three layers of magnetic films having different composition components are laminated on a substrate via at least a heat dissipation layer, and a dielectric film having a predetermined thickness is formed on these structures, and then information is recorded. The present invention provides a method for forming a magneto-optical recording medium in which a magnetic film in a non-performing region is nitrided and a material constituting the dielectric film is further laminated on these structures.
A step of laminating a first dielectric film, a heat dissipation layer, and a second dielectric film in this order on the substrate; and a first magnetic film and a first magnetic film on the second dielectric film. Laminating a second magnetic film having a low Curie temperature and a third magnetic film having a domain wall coercive force larger than that of the first magnetic film and having a Curie temperature higher than that of the second magnetic film in this order; A step of laminating a fourth dielectric film having a predetermined thickness on the film; a step of nitriding at least the third magnetic film in a region where information is not recorded; and the nitrided third magnetic film and fourth dielectric And a method of forming a magneto-optical recording medium including a step of laminating a third dielectric film on the body film.
According to this, manufacturing of the magneto-optical recording medium can be facilitated and manufacturing cost can be reduced.
The present invention also includes at least a first magnetic film having a relatively small domain wall coercivity, a second magnetic film having a relatively low Curie temperature, and a relatively high domain wall coercivity and a high Curie temperature. A magneto-optical recording medium in which three magnetic films are laminated in this order, wherein the third magnetic film existing at least in a region where no information is recorded is selectively nitrided. It is to provide.
According to this, it is possible to stabilize the reproduction characteristics of the magneto-optical recording medium and improve the CNR.

FIG. 1 is a block diagram of an embodiment of the magneto-optical recording medium of the present invention.
FIG. 2 is a schematic sectional view of an embodiment of the magneto-optical recording medium of the present invention.
FIG. 3 is an explanatory view of the main part of the manufacturing process of one embodiment of the magneto-optical recording medium of the present invention.
FIG. 4 is a graph showing the relationship between the film thickness of the fourth dielectric film and the CNR when a land-groove substrate is used in the magneto-optical recording medium of the present invention.
FIG. 5 is a graph showing the relationship between the film thickness of the fourth dielectric film and the CNR when a groove substrate is used in the magneto-optical recording medium of the present invention.
FIG. 6 is a graph showing the relationship between the film thickness of the fourth dielectric film and the CNR when a land substrate is used in the magneto-optical recording medium of the present invention.
FIG. 7 is a block diagram of a conventional magneto-optical recording medium.

The present invention intends to facilitate manufacturing, reduce manufacturing cost, and improve CNR characteristics by nitriding a magnetic layer in a region where information is not required to be recorded in a magneto-optical recording medium.
In the method for forming a magneto-optical recording medium according to the present invention, the nitriding step may be performed by leaving the medium after the fourth dielectric film is laminated in a nitrogen atmosphere at room temperature for a predetermined time.
Further, as the substrate, a substrate in which a plurality of lands and grooves are alternately formed on the surface can be used. In this case, a boundary portion between adjacent lands and grooves is an inclined surface, and the inclined surface is It is an area where information is not recorded, and the fourth dielectric film may be laminated on the third magnetic film on the land and the groove to the extent that the fourth dielectric film is not laminated on the inclined surface. .
Further, when a substrate having a plurality of grooves formed on the surface is used as the substrate, the boundary portion between adjacent grooves is constituted by a convex side wall surface, and the side wall surface is an area where information is not recorded. The fourth dielectric film may be laminated on the third magnetic film on the groove to the extent that the fourth dielectric film is not laminated on the side wall surface.
Further, when a substrate having a plurality of lands formed on the surface is used as the substrate, the boundary portion between adjacent lands is composed of concave side grooves, and the side grooves are areas where information is not recorded, and the side grooves The fourth dielectric film may be laminated on the third magnetic film on the land so that the fourth dielectric film is not laminated.
In the present invention, the “domain wall coercive force” refers to a force required to move a magnetic wall formed at the boundary between magnetic domains in the magnetic film. For example, the harder the magnetic wall is moved, the greater the domain wall coercivity.
Each layer formed on the substrate can be formed by sputtering a target of various materials arranged in a sputtering apparatus with a sputtering gas.
The present invention will be described in detail below based on the embodiments shown in the drawings. However, this does not limit the present invention.
<Configuration of magneto-optical recording medium>
FIG. 1 shows a block diagram of an embodiment of the magneto-optical recording medium of the present invention.
As shown in FIG. 1, the magneto-optical recording medium of the present invention is
On the substrate 1, a first dielectric film 2, a heat dissipation layer 3, a second dielectric film 4, a first magnetic film 5, a second magnetic film 6, a third magnetic film 7, a fourth dielectric film 81, and A third dielectric film 82 is formed in this order.
An example of the film thickness and material of each layer is shown below.
Substrate 1: 1.2 mm; glass first dielectric film 2: 5 nm; SiN
Heat dissipation layer 3: 30 nm; Ag
Second dielectric film 4: 30 nm; SiN
First magnetic film 5: 60 nm; Tb ₂₇ Fe ₅₇ Co ₁₆
Second magnetic film 6: 10 nm; Tb ₂₀ Fe ₇₉ Co ₁
Third magnetic film 7: 30 nm; Gd ₂₇ Fe ₆₂ Co ₁₁
Fourth dielectric film 81: 2 nm; SiN
Third dielectric film 82: 53 nm; SiN
The material of each of the above layers is an example, and other materials may be adopted as necessary. The medium of this embodiment is a medium (front surface medium) that irradiates light from the third dielectric film 82 side, which is different from the substrate.
Of course, the medium configuration of the present invention can also be applied to a type of medium in which light is incident from the normally used substrate 1 side. In this case, the materials of the first magnetic film 5 and the third magnetic film 7 and The film thickness is reversed.
The front surface medium that irradiates light from the third dielectric film side can reach the magnetic film without going through the thick substrate, so that the objective lens can be made smaller than the medium that irradiates light from the substrate side. Can also be densified.
As the substrate 1 of the present invention, in addition to glass, a material for HDD (Hard Disk Drive) such as an Al alloy or Si may be used.
As the first dielectric layer _{2, C, SiO 2, Y} -SiO 2, AlN or the like.
As the second dielectric film 4, oxides or nitrides such as C, SiO ₂ , Y—SiO ₂ , ZnSiO ₂ , AlO, and AlN may be used.
As the third and fourth dielectric films 81 and 82, oxides or nitrides such as SiO ₂ , ZnSiO ₂ , AlO, and AlN may be used.
As the heat dissipation layer 3, an Al alloy such as AlTi and AlCr, an alloy mainly composed of Ag, Au, Pt, and these metals may be used.
The first magnetic film 5 may use rare earth-transition metals such as DyFeCo and TbDyFeCo in addition to TbFeCo.
The second magnetic film 6 may use a rare earth-transition metal such as DyFeCo and TbDyFeCo in addition to TbFeCo.
The third magnetic film 7 may use a rare earth-transition metal such as GdFeCoAl, GdTbFeCo, GdDyFeCo in addition to GdFeCo.
Here, the material and composition of the first magnetic film 5 are selected so that the domain wall coercive force is relatively higher than that of the third magnetic film 7.
The material and composition of the second magnetic film 6 are selected so that the Curie temperature is lower than that of the first and third magnetic films (5, 7).
The material and composition of the third magnetic film 7 are selected so that the domain wall coercive force is lower and the Curie temperature is higher than those of the first and second magnetic films (5, 6).
In FIG. 1, the third and fourth dielectric films (81, 82) are both SiN and differ only in film thickness.
However, as will be described later, the third dielectric film 82 is formed after the relatively thin fourth dielectric film 81 is formed and the first to third magnetic layers (5, 6, 1) are nitrided. Form. The reason why the third and fourth dielectric films are not formed at a time is that when a thick dielectric film of about 55 nm is formed on the magnetic film, the underlying magnetic film cannot be sufficiently nitrided.
Further, the film thickness of the fourth dielectric film 81 is not formed in the area where information is not recorded, and the magnetic layer in the area where information is recorded is not nitrided while sufficiently ensuring the CNR of the area where information is recorded. Thickness. For this reason, the thickness of the fourth dielectric film 81 is preferably in the range of 1 to 10 nm.
For enhancement, the thicknesses of both dielectric films may be adjusted so that the total thickness of the fourth dielectric film 81 and the third dielectric film 82 is about 55 nm. Further, the total film thickness may be adjusted for adjusting optical and thermal conditions.
The magneto-optical recording medium of the present invention shown in FIG. 1 can be applied to any of (a) land-groove substrate, (b) groove substrate, and (c) land substrate. In particular, when the laser annealing treatment was performed as in the conventional medium, the magnetic layer on the land or groove was lost, so (a) the land-groove substrate could not be used. Then, since (a) a land-groove substrate can be used, a high-density magneto-optical recording medium can be provided.
FIG. 2 is a schematic sectional view of a magneto-optical recording medium formed on three substrates in one embodiment of the present invention.
Here, for the sake of explanation, the first dielectric film 2 to the third magnetic film 7 shown in FIG. 1 are not distinguished from each other, but a layer structure is actually formed.
Further, although the fourth and third dielectric films (81, 82) are formed on the third magnetic layer 7, this is not a drawing reflecting an accurate film thickness.
FIG. 2A shows the case of a land-groove substrate. The flat portions of the land 21 and the groove 22 are information recording areas, and the magnetic film formed on the land 21 and the groove 22 in this area. Information is recorded / reproduced at (5, 6, 7).
Further, the boundary portion between the land 21 and the groove 22, that is, the magnetic films (5, 6, 7) in the inclined surface area A and area B shown in FIG. This area is not played back. Since the areas A and B where information is not recorded / reproduced are nitrided, the information recording area of the land 21 and the information recording area of the groove 22 are magnetically separated, and the reliability at the time of reproducing information is improved. Can do.
FIG. 2B shows a groove substrate, but a flat portion of the adjacent groove 22 is formed by nitriding the magnetic film in the region A and the region B formed on the surface of the convex side wall surface portion. Are magnetically separated.
In FIG. 2B, the flat portion of the groove 22 (track pitch of about 0.4 μm) is an information recording area, and the convex side wall surface is not used as a recording area but is used for a servo track.
FIG. 2C shows a land substrate. By nitriding the magnetic films (5, 6, 7) in the regions A and B formed in the concave side grooves, the adjacent lands 21 are flattened. The parts are magnetically separated.
In FIG. 2C, the flat portion of the land 21 (track pitch of about 0.4 μm) is an information recording area, and the concave side groove is not used as a recording area but is used for a servo track.
<Method of forming magneto-optical recording medium>
Next, a method for forming each layer of the medium according to the embodiment of the present invention will be described.
First, a substrate 1 having any surface shape as shown in FIG. 2 is prepared. Here, the board | substrate 1 can be formed using plastics, such as a metal and PC (polycarbonate).
Next, in order to form each layer (2-82) on the substrate shown in FIG. 1, the substrate 1 is set at a predetermined position in the DC magnetron sputtering apparatus.
Then, a target necessary for forming each layer is disposed at a position facing the substrate 1, and reactive sputtering is sequentially performed in a reactive gas atmosphere such as Ar gas.
Reactive sputtering is performed by placing the substrate 1 on a table that rotates in the vicinity of the target while revolving, or while rotating the target while the substrate is fixed. Reactive sputtering is performed at room temperature.
FIG. 3 shows the main part of the formation process of the magneto-optical recording medium of the first embodiment of the present invention.
Although FIG. 3 shows a cross-sectional structure when a land-groove substrate is used, the order and conditions of the forming steps are the same for the groove substrate and the land substrate. Since the surface shapes of the substrates are different, the laminated structure is different, but the areas to be nitrided are all areas that are not recorded.
Each layer of the first embodiment is formed in the following order.
[Step 1] Formation of first dielectric film 2 Target: Si
Sputtering gas: Ar gas, N ₂ gas Flow rate ratio: Ar: N ₂ = 2: 1
Gas pressure: 0.3Pa
Input power: 0.5 kW
Under the above conditions, SiN as the first dielectric film 2 is formed on the substrate 1 with a thickness of about 5 nm.
[Step 2] Formation of heat dissipation layer 3 Target: Ag
Sputtering gas: Ar gas Gas pressure: 0.1 Pa
Input power: 0.5 kW
Under the above conditions, an Ag film as the heat dissipation layer 3 is formed on the first dielectric film 2 with a thickness of about 30 nm.
[Step 3] Formation of second dielectric film 4 Target: Si
Sputtering gas: Ar gas, N ₂ gas Flow rate ratio: Ar: N ₂ = 2: 1
Gas pressure: 0.3Pa
Input power: 0.5 kW
Under the above conditions, SiN as the second dielectric film 4 is formed on the heat dissipation layer 3 with a thickness of about 30 nm.
[Step 4] Formation of the first magnetic film 5 Target: Alloy target of Tb27Fe57Co16 Sputtering gas: Ar gas Gas pressure: 0.5 Pa
Input power: 0.5 kW
Under the above conditions, Tb27Fe57Co16 as the first magnetic film 5 is formed on the second dielectric film 4 to a thickness of about 60 nm. Here, the Curie temperature of the first magnetic film 5 is 260 degrees, which is higher than the second magnetic film 6 to be formed next.
[Step 5] Formation of second magnetic film 6 Target: Alloy target of Tb20Fe79Co1 Sputtering gas: Ar gas Gas pressure: 0.5 Pa
Input power: 0.5 kW
Under the above conditions, Tb20Fe79Co1 as the second magnetic film 6 is formed on the first magnetic film 5 to a thickness of about 10 nm. Here, the Curie temperature of the second magnetic film 6 is about 130 degrees, which is lower than that of the first and third magnetic films (5, 7).
[Step 6] Formation of third magnetic film 7 Target: Alloy target of Gd27Fe62Co11 Sputtering gas: Ar gas Gas pressure: 0.5 Pa
Input power: 0.5 kW
Under the above conditions, Gd27Fe62Co11 as the third magnetic film 7 is formed on the second magnetic layer 6 with a film thickness of about 30 nm. Here, the Curie temperature of the third magnetic film 7 is 240 degrees, which is higher than that of the second magnetic film 6.
The composition ratio of the first, second, and third magnetic films is not limited to the above composition ratio, and the Curie temperature of the first and third magnetic films (5, 7) is the Curie of the second magnetic film 6. What is necessary is just to select the composition ratio of each magnetic layer so that it becomes higher than temperature and becomes a domain wall motion type.
FIG. 3A shows a schematic cross-sectional view after the first dielectric film 2 to the third magnetic film 7 are formed on the substrate 1. Here, the magnetic film (5, 6, 7) is also formed at the boundary portion between the land and the groove, that is, the portion where information is not recorded. However, since this boundary portion is an inclined surface, information is recorded. The land 21 and the groove 22 are formed with a film thickness thinner than the flat portions.
The thin film thickness of the magnetic film or the like on the inclined surface is considered to be due to the directivity of the sputtered particles when reactive sputtering is performed. In general, in a magnetron sputtering apparatus, in order to uniformly form a film on a flat portion of a substrate, sputtered particles fly vertically from above the substrate. That is, in a sputtering apparatus having a strong vertical directivity, the number of particles that frequently fly on the inclined surface and fly in an oblique direction is small, so that the thickness of the inclined surface becomes thin.
[Step 7] Formation of fourth dielectric film 81 Target: Si
Sputtering gas: Ar gas, N ₂ gas Flow rate ratio: Ar: N ₂ = 2: 1
Gas pressure: 0.3Pa
Input power: 0.5 kW
Under the above conditions, SiN as the fourth dielectric film 81 is formed on the third magnetic film 7 to a thickness of about 2 nm. Here, the thickness of the fourth dielectric film 81 is such that the portion of the magnetic film (5, 6, 7) that is not the recording area is sufficiently large that the adjacent recording area is magnetically separated by the next nitriding process. It is necessary to select such that it is nitrided to 1 nm, and it is not limited to 2 nm.
The fourth dielectric film 81 is also somewhat laminated on the inclined surface of the boundary portion. However, due to the vertical directivity of the sputtering apparatus as described above, the fourth dielectric film 81 is considerably thinner on the inclined surface than the flat portion of the land and groove. It is formed.
Further, when the fourth dielectric film 81 is formed, the fourth dielectric film 81 is formed under the condition that the directivity in the vertical direction of the sputtered particles is strictly controlled and the tilt angle of the substrate is optimized. It can control so that the sputtered particle to form hardly adheres to an inclined surface.
FIG. 3B shows a cross-sectional view after the fourth dielectric film 81 is formed. As shown in the figure, the fourth dielectric film 81 is formed on the flat portion of the land 21 and the groove 22 like the other layers (2 to 7), but the boundary portion between the land and the groove (inclined surface). ) Can hardly be formed. For this reason, in the nitriding process in the next step 8, the boundary portion where the fourth dielectric film 81 is not formed, that is, the magnetic film at the inclined surface portion is nitrided.
As will be described later, in order to ensure a CNR equal to or higher than that of a conventional magneto-optical recording medium, the thickness of the fourth dielectric film 81 is set to about several nm (1 to 10 nm). preferable. In particular, in the case of a land-groove substrate, for example, the thickness of the fourth dielectric film 81 is preferably about 2 to 5 nm in order to obtain a CNR of 45 dB or more.
[Step 8] Nitriding treatment of magnetic film The medium after step 7 is subjected to nitriding treatment by introducing N ₂ gas having a gas pressure of 1.0 Pa into the sputtering apparatus and leaving it at room temperature for about 5 minutes.
Here, although each magnetic film (5, 6, 7) is laminated | stacked on both the flat part and boundary part of a land-groove board | substrate, for example, since a boundary part is an inclined surface, each magnetic film The film thickness is thinner than the flat part. Further, the fourth dielectric film is not laminated at the boundary portion. Therefore, the magnetic film at the thin boundary portion (regions A and B in FIG. 2) is nitrided.
In addition, if the medium is exposed to an atmosphere of N ₂ gas for an excessively long time, nitridation proceeds in a portion of the recording area that is not desired to be nitrided.
Therefore, the land-groove substrate land-to-groove boundary portion (inclined surface), the convex side wall surface of the groove substrate, or the concave side groove region of the land substrate may be left for a period of time that is nitrided. Since it is preferable, the leaving time is not limited to 5 minutes.
FIG. 3C shows a cross-sectional view after nitriding. By this nitriding treatment, the magnetic films (5, 6, 7) existing at the boundary portion between the land 21 and the groove 22 are nitrided to form nitride films 25, 26.
In the portions of the nitride films 25 and 26, magnetism has disappeared, so information cannot be recorded. Therefore, the magnetic films (5, 6, 7) on the flat portion of the adjacent land 21 and the flat portion of the groove 22 are magnetically separated by the nitride films 25, 26.
The magnetic film is composed of three layers (5, 6, 7). In order to magnetically separate the magnetic films in the adjacent recording areas, at least the third magnetic film 7 may be nitrided. Therefore, an appropriate standing time may be selected in consideration of the film thickness of the laminated magnetic films (5, 6, 7) and the fourth dielectric film 81, required recording characteristics, and the like.
[Step 9] Formation of third dielectric film 82 Target: Si
Sputtering gas: Ar gas, N ₂ gas Flow rate ratio: Ar: N ₂ = 2: 1
Gas pressure: 0.3Pa
Input power: 0.5 kW
Under the above conditions, SiN as the third dielectric film 82 is formed on the fourth dielectric film 81 to a thickness of about 53 nm. Here, the film thickness is not limited to 53 nm, but may be set so that the total thickness of the fourth dielectric film 81 is about 55 nm.
If the fourth dielectric film 81 is formed between 1 and 10 nm, the third dielectric film 82 may be formed at about 54 to 45 nm.
Through the above steps 1 to 9, the magneto-optical recording medium of the present invention as shown in FIG.
This forming process does not include a laser annealing process as in the past, and all processes except nitriding are reactive sputtering performed at room temperature, so the forming process can proceed smoothly and manufacturing costs can be reduced. can do. In addition, the regeneration characteristics are not deteriorated later as in the oxidation treatment, and the highly stable regeneration can be performed.
<Reproduction characteristics of magneto-optical recording media>
Next, the reproduction characteristics of the magneto-optical recording medium of the present invention will be described.
In order to examine the reproduction characteristics, the following evaluation experiment was conducted.
Evaluation apparatus: spectrum analyzer Optical system: objective lens NA = 0.85, wavelength 405 nm
Recording: Laser strobe magnetic field modulation recording method Recording frequency 50 MHz (= 0.15 μm)
Evaluation value: CNR (signal-to-noise ratio dB)
For comparison, in the conventional medium shown in FIG. 7, the third dielectric film 8 was formed without laser annealing of the magnetic film in the region not recorded after the formation of the third magnetic film 7 and laser annealing. Created something.
As a conventional medium subjected to laser annealing, a groove substrate and a land substrate were used, and as a conventional medium not subjected to laser annealing, three kinds of substrates including a land-groove substrate were used.
Further, in the conventional medium, the first dielectric film 2 to the third magnetic layer 7 formed on the substrate 1 are the same as the conditions shown in the steps 1 to 6 in the forming process of the present invention and the same. It was formed with a film thickness. The third dielectric film 8 was formed to have a film thickness of 53 nm under the same conditions as in Step 9.
In the case of performing laser annealing, laser annealing was performed by irradiating a region of the third magnetic layer 7 where recording was not performed with a high-power laser before the formation of the third dielectric film 8.
In the medium of the present invention, in order to confirm the effect of the nitriding treatment, the nitriding treatment time is fixed to 5 minutes, and the thickness of the fourth dielectric film 81 is changed from 1 nm to 10 nm in 1 nm units. Was created respectively.
FIG. 4 shows the CNR (dB) at the time of reproduction of the medium of the present invention when a land-groove substrate is used, FIG. 5 shows the CNR (dB) when a groove substrate is used, and FIG. CNR (dB) is shown. In either case, the horizontal axis represents the film thickness (nm) of the fourth dielectric film 81.
(A) Reproduction Characteristics of Land-Groove Substrate First, in the case of a land-groove substrate, a conventional medium not subjected to laser annealing does not cause domain expansion during reproduction because the domain wall is not separated, resulting in reproduction failure.
On the other hand, in the medium of the present invention, as shown in FIG. 4, when the thickness of the fourth dielectric film 81 is 1 nm and 10 nm, the CNR is about 37 dB, which is slightly bad, but in the range of 2 nm to 7 nm, the CNR = 42 to 46 dB, showing practical numerical values.
In particular, when the thickness of the fourth dielectric film 81 was 2 nm, CNR = 45.5 dB was shown, the magnetic domain was sufficiently expanded, and the effect of nitriding was the greatest.
If the film thickness of the fourth dielectric film 81 is about 1 nm or less, it is highly possible that the land and the flat portion of the recording area are also nitrided, so the CNR is considered to be low.
Further, when the film thickness is 10 nm or more, it is considered that the fourth dielectric film 81 is also laminated on the inclined surface that is the boundary portion between the land and the groove, and the nitriding treatment at this boundary portion is insufficient. It is considered that the separation of the magnetic film is incomplete and the CNR is lowered.
Therefore, in the case of a land-groove substrate, if an appropriate value in the range of 2 nm to 7 nm is selected for the thickness of the fourth dielectric film 81, stable domain expansion occurs during reproduction, and a practically good CNR can be obtained. it can.
(B) Reproduction characteristics of the groove substrate Next, in the case of the groove substrate, in the conventional medium not subjected to laser annealing, magnetic domain expansion during reproduction did not occur, resulting in reproduction failure.
In addition, the conventional medium subjected to laser annealing can be reproduced by expanding the magnetic domain, and the CNR was 43.0 dB.
On the other hand, in the medium of the present invention, as shown in FIG. 5, when the film thickness of the fourth dielectric film 81 was in the range of 2 to 5 nm, the CNR was higher than the CNR of the conventional medium. In particular, according to FIG. 5, when the film thickness was 3 nm, CNR = 46.0 dB, and the effect of nitriding was the greatest.
Therefore, also in the case of a groove substrate, if the film thickness of the fourth dielectric 81 of the medium of the present invention is appropriately selected, stable magnetic domain expansion occurs during reproduction, and a practically good CNR can be obtained.
(C) Reproduction characteristics of land substrate Next, in the case of a land substrate, in the conventional medium not subjected to laser annealing, magnetic domain expansion during reproduction did not occur, resulting in reproduction failure.
Further, in the conventional medium subjected to laser annealing, reproduction by magnetic domain expansion was possible, and the CNR was 42.5 dB.
On the other hand, in the medium of the present invention, as shown in FIG. 6, a CNR higher than the CNR of the conventional medium was obtained when the thickness of the fourth dielectric film 81 was in the range of 2 to 6 nm. In particular, according to FIG. 6, when the film thickness was 3 nm, CNR = 45.5 dB, and the nitriding effect was the greatest.
Therefore, in the case of a land substrate as well, if the film thickness of the fourth dielectric film 81 is appropriately selected, stable magnetic domain expansion occurs during reproduction, and a practically good CNR can be obtained.
As described above, in the magneto-optical recording medium of the present invention, after a dielectric film having a predetermined thickness is formed on the laminated magnetic film, a portion of the magnetic film that is not the information recording area is nitrided. Therefore, a practically good CNR can be obtained with stable reproduction characteristics.
Also, unlike the conventional media, there is no need for a laser annealing process, so the manufacturing process can be simplified and the manufacturing cost can be reduced, and the domain walls are separated by nitriding. A magneto-optical recording medium with more stable reproduction characteristics and no deterioration can be provided.
Furthermore, the medium having a laminated structure according to the present invention can be applied to a land-groove substrate, and can reduce the manufacturing cost and improve the reproduction characteristics in a high-density medium.

Claims (3)

Three layers of first, second, and third magnetic films having different composition components are laminated on a substrate via at least a heat dissipation layer, and a fourth dielectric film having a predetermined thickness is formed on these structures. Then, a magnetic film in a region where no information is recorded is nitrided, and a third dielectric film made of the same material as that constituting the fourth dielectric film is further laminated on these structures, and the third dielectric A method of forming a magneto-optical recording medium for recording information by entering light from a film side ,
The substrate is a substrate in which a plurality of lands and grooves are alternately formed on the surface, a boundary portion between adjacent lands and grooves is an inclined surface, and the inclined surface is an area where information is not recorded, and this inclined A fourth dielectric film is laminated on the third magnetic film on the land and the groove to such an extent that the fourth dielectric film is not laminated on the surface;
A first step of laminating a first dielectric film, a heat dissipation layer, and a second dielectric film in this order on a substrate; and a first magnetic film and a first magnetic film on the second dielectric film. A second step of laminating a second magnetic film having a low Curie temperature and a third magnetic film having a domain wall coercive force lower than that of the first magnetic film and having a Curie temperature higher than that of the second magnetic film in this order; A third step of laminating a fourth dielectric film having a predetermined thickness on the three magnetic films, a fourth step of nitriding at least the third magnetic film in a region where information is not recorded, and the nitrided third step A method of forming a magneto-optical recording medium , comprising: performing a fifth step of laminating the third dielectric film on the magnetic film and the fourth dielectric film in this order . Three layers of first, second, and third magnetic films having different composition components are laminated on a substrate via at least a heat dissipation layer, and a fourth dielectric film having a predetermined thickness is formed on these structures. Then, a magnetic film in a region where no information is recorded is nitrided, and a third dielectric film made of the same material as that constituting the fourth dielectric film is further laminated on these structures, and the third dielectric A method of forming a magneto-optical recording medium for recording information by entering light from a film side,
The substrate is a substrate in which a plurality of grooves are formed on the surface, and a boundary portion between adjacent grooves is constituted by a convex side wall surface, and the side wall surface is a region in which information is not recorded. The fourth dielectric film is laminated on the third magnetic film on the groove to the extent that the fourth dielectric film is not laminated,
A first step of laminating a first dielectric film, a heat dissipation layer, and a second dielectric film in this order on a substrate; and a first magnetic film and a first magnetic film on the second dielectric film. A second step of laminating a second magnetic film having a low Curie temperature and a third magnetic film having a domain wall coercive force lower than that of the first magnetic film and having a Curie temperature higher than that of the second magnetic film in this order; on the third magnetic film, a third step and a fourth step of at least nitriding said third magnetic film in the region that does not record information, the third nitrided for laminating the fourth dielectric film having a predetermined thickness on the magnetic film and the fourth dielectric film, forming method of the magneto-optical recording medium and a fifth step which comprises carrying out in the order of laminating the third dielectric film. Formation of the fourth step, the fourth medium after the dielectric layer is deposited, according to claim 1 or 2 of the magneto-optical recording medium characterized in that it is carried out is left for a predetermined time in room temperature and nitrogen atmosphere Method.

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